Today's high-efficiency particulate arrestance (HEPA) filters do not have the capability to deal with all aspects of indoor air pollution. Although HEPA filters may be effective at filtering out as much as 99.97% of air borne particles that have a size of 0.3 μm or larger, they are not always effective at treating or removing airborne contaminants made up of microorganisms, viruses, and bacteria smaller than 0.3 μm, all of which are potentially harmful. The inventions disclosed herein, through new devices for and new methods of producing Reactive Oxygen Species (“ROS”), have the ability to treat and remove airborne contaminants using processes that produce a non-thermal plasma field from ambient air within a reaction chamber.
One of ordinary skill in the art would understand “non-thermal plasma” to refer to plasma that is not in thermodynamic equilibrium. In particular, as used herein, “non-thermal plasma” refers to plasma that is produced by a process that does not involve the use or generation of substantial heat; in other words, the temperature of the fluid used to generate the plasma (e.g., ambient air) is not substantially increased during the process of generating plasma. It is known in the art that non-thermal plasma contains reactive forms of oxygen, i.e., ROS, that have a much higher reactivity than oxygen in the form of stable oxygen molecules, which include atomic oxygen, singlet oxygen, hydrogen peroxide, superoxide anion, tri-atomic oxygen and hydroxyl radicals. It is known that ROS can react with particles as small as and smaller than about 0.3 microns. The antimicrobial properties of ROS in the air and on surfaces is known, and the mechanisms by which ROS inactivate bacteria has been studied. See, e.g., Suresh G. Joshi, M. Cooper, A. Yost, M. Paff, U. K. Ercan, G. Fridman, G. Friedman, A. Fridman, and A. D. Brooks, “Nonthermal dielectric-barrier discharge plasma-induced inactivation involves oxidative DNA damage and membrane lipid peroxidation in Escherichia coli,” Antimicrobial Agents Chemotherapy, vol. 55, no. 3, pp. 1053-1062, March 2011 (which article is incorporated by reference in its entirety into this application). It is understood, for example, that the different ROS attach themselves to the surfaces of contaminants and other pathogens at bond sites to create strong oxidizing radicals. These radicals draw out the hydrogen that is present in these contaminants and other pathogens, breaking down the surface membranes and rendering them inactive (in other words, neutralizing the contaminants and pathogens). The end result may be that the hydroxide and hydrogen radicals combine and form water, and the contaminants and pathogens are inactivated and neutralized. Viruses, however, are bundles of nucleic acid surrounded by a protein bases capsid. When viruses are exposed to ROS both the capsid and viral RNA can be destroyed.
Furthermore, the ROS generated in the non-thermal plasma fields described herein can also breakdown Volatile Organic Compounds (VOC). When carbon based VOCs (alcohols, aldehydes, and ketones) pass through the non-thermal plasma, the covalent bonds in the molecules can be broken, which can also produce carbon dioxide and/or oxygen.
Unlike many other low energy technologies, the present invention avoids producing toxic intermediates. The inventions disclosed herein can be used for food preservation, in medical applications, and other industries in which airborne contaminants can be problematic.